Claude Code: fix: handle None message in interact endpoint

app.py

@@ -90,7 +90,7 @@ async def interact(request: InteractRequest):
     this would connect to the OpenClaw agent system.
     """
     try:
-        msg_preview = request.message[:100] if len(request.message) > 100 else request.message
+        msg_preview = (request.message[:100] if len(request.message) > 100 else request.message) if request.message else ""
         logger.info(f"Interact request: {msg_preview}...")
 
         # Placeholder response - in production, this would call the agent brain